French Onion Green Bean Casserole: An Elevated Classic

Ingredients

• 2 tablespoons butter
• 2 large yellow onions, thinly sliced lengthwise
• salt and ground black pepper to taste
• 1 tablespoon sherry vinegar
• 2 tablespoons butter
• 2.5 tablespoons all-purpose flour
• 2.5 cups milk
• 1 pinch ground nutmeg
• 1 pinch cayenne pepper to taste
• 0.25 teaspoon ground thyme
• 2 tablespoons melted butter
• 0.67 cup panko bread crumbs
• 2 pounds fresh green beans, trimmed
• 4 ounces shredded Gruyere cheese, divided
• 0.33 cup grated Parmesan cheese

Instructions

1. Gather all ingredients. Preheat your oven to 375 degrees F (190 degrees C). Grease a 9x13-inch casserole dish for easy serving.
2. Melt 2 tablespoons of butter in a large skillet over medium heat. Add the sliced onions to the pan and cook, stirring occasionally, until they are very soft and deeply golden brown, approximately 15 minutes. Stir in sherry vinegar to deglaze the pan. Transfer the caramelized onions to a small bowl and set aside.
3. In the same skillet, melt an additional 2 tablespoons of butter. Whisk in 2 tablespoons of all-purpose flour. Cook over medium heat, stirring constantly, until the mixture smells subtly like baked pie crust, about 3 minutes. This creates a roux that will thicken the sauce.
4. Gradually whisk in the milk, about 1/2 cup at a time, ensuring each addition is fully incorporated before adding more. Whisk in nutmeg, cayenne pepper, and dried thyme. Bring the mixture to a simmer and cook until thickened, whisking constantly, for approximately 3 more minutes. Transfer the white sauce to a bowl and set aside.
5. Melt the remaining 2 tablespoons of butter in the now-clean skillet. Stir in the panko breadcrumbs until they are evenly coated in the melted butter. Set aside for topping the casserole.
6. Bring a large saucepan of salted water to a boil over medium-high heat. Add the fresh green beans and boil until they are bright green and crisp-tender, about 3 to 4 minutes. Drain the green beans thoroughly.
7. Spoon half of the caramelized onions into the prepared casserole dish, creating an even layer. Top with the drained green beans. Season generously with salt and freshly ground black pepper. Spread the reserved white sauce evenly over the green beans. Sprinkle with half of the shredded Gruyere cheese. Top with the remaining caramelized onions, gently pressing them down into the sauce and cheese. Sprinkle the buttered panko breadcrumbs evenly over the top, followed by the remaining Gruyere cheese and grated Parmesan cheese.
8. Bake in the preheated oven until the casserole is heated through and the topping is lightly browned and bubbly, about 30 minutes. Let the casserole rest for 10 minutes before serving to allow it to set slightly.
9. Serve the French Onion Green Bean Casserole and enjoy!

Nutrition

• Calories: 217 kcal
• Fat Content: 13 g
• Fiber Content: 4 g
• Sugar Content: 6 g
• Sodium Content: 195 mg
• Protein Content: 9 g
• Cholesterol Content: 38 mg
• Carbohydrate Content: 19 g
• Saturated Fat Content: 8 g
• Unsaturated Fat Content: 0 g